lib: Remove hardcoded size of readable pcrs values
lib: Remove hardcoded size of readable pcrs values

There is no rationale on why pcrs struct shall always
be 24 in size, hence relying on the internal buffer size
instead

Signed-off-by: sebastien le stum <eab1024c437ed3bd6a7c8a3a281fc7d29e1067e0@gmail.com>

01org/tpm2.0-tools,01org/tpm2.0-tools,01org/tpm2.0-tools